The operator of coal-fired steam locomotives in the tourist spot of Nikko in eastern Japan is trialing a biofuel as a way to cut its carbon dioxide emissions, the first such initiative in the country. Tobu Railway Co. said it started the trial, set to last around one year, on Jan. 31, partially replacing the coal used by its SL Taiju locomotives with biocoke, made from buckwheat chaff, wood chips, coffee grounds and other materials. Biocoke will be substituted for around 40 percent of the 160 tons of coal burned each year to keep boiler pressure constant on the company’s three Taiju engines, i…